Liquid crystals represent a novel state of matter intermediate between the crystalline and isotropic liquid states of matter. This unique behavior may lead to a variety of useful applications including the use of such materials in electrooptical devices, in thermography, etc.
Liquid crystalline (LC) polymers combine the desirable properties of macromolecules with the anisotropic properties of liquid crystals. An important application of LC polymers includes the formation of high tensile strength fibers. Another end use is the blending of such LC polyesters with existing polymers for the production of molecular composites.
Certain monomers containing the biphenyl mesogen, as depicted in FIG. 1, which can be used to form liquid crystalline polyesters are known. Specifically, the monomer where r=2 is identified by CAS Registry No. 20994-26-7 whereas r=6 is identified by CAS Registry No. 97087-90-6. A computer search revealed the following references which appear to show the synthesis and use of one or both of these monomers as follows:
1. Sato, M. et al., "Synthesis and Liquid-Crystalline Properties of Thermotropic Homo- and Copolycarbonates", J. Polym. Sci., Part A: Polym. Chem., 26(11) 3077-3088 (1988) appears to name both monomers. The homo- and copolycarbonates described have flexible spacers between mesogens and between the carbonate linkages.
2. The monomer where r=6 is mentioned in "Combined Liquid-Crystalline Polymers with Chiral Phases 2. Lateral Substituents", by H. Kapitza et al., Makromol. Chem. 189(8) 1793-1807 (1988). The polyester-polyether polymers described therein have mesogenic groups in the main chain as well as in the side groups.
3. The monomer where r=2 is mentioned in U.S. Pat. No. 4,791,187.
4. Both monomers (r=2 and r=6) are mentioned in "Liquid Crystalline Behavior of Central Core-Type Model Compounds for Thermotropic Polycarbonates", by M. Sato et al., Makromol. Chem., Rapid Comm., 8(8), 383-386 (1987). The thermotropic polycarbonates were prepared by reaction of omega, omega'-(4,4'-biphenylenedioxy)dialkanols with n-alkyl or phenylchlorocarbonate.
5. M. Sato et al. in "New Liquid-Crystalline Polycarbonates from Diols Containing a Biphenyl Ring Sequence As Central Core", Makromol. Chem., Rapid Commun., 7(4), 231-234 (1986) mentions liquid crystal polycarbonates prepared by melt condensation of 6,6'-(4,4'-biphenylenedioxydihexanol (the monomer when r=6) and alkylene di-phenyl dicarbonates in the presence of zinc acetate.
6. B. Reck et al., in "Combined Liquid Crystalline Polymers: Mesogens in the Main Chain and as Side Groups", Makromol. Chem., Rapid Commun., 6(4), 291-299 (1985) shows the preparation and polymerization of the monomers where r=2 and 6 with phenylazophenoxy or biphenyloxy group containing diethyl malonate derivatives.
7. M. Kawaguchi et al. in "Synthesis and Physical Properties of Polyfunctional Methacrylates. Part 4. Synthesis and Physical Properties of Aromatic Dimethacrylate Copolymers", Dent Mater. J., 3(2), 272-279 (1984) describes copolymers of methyl methacrylate and dimethacrylates of various dihydroxy compounds, including 4,4'-(2-hydroxyethoxy) biphenyl as possible dental resonance materials. The monomer where r=2 was prepared and esterified with methacryloyl chloride.
8. Japanese Kokai No. 58/217553 (abstracted in Chem. Abstr. 101:39330m) describes thermoplastic resin compositions including those containing the methylenedianiline terminated monomer where r=2.
9. U.S. Pat. No. 3,562,335 describes 4,4'-dialkoxybiphenyls and in its disclosure shows preparation of the monomer where r=2.
More recently, U.S. Pat. No. 4,833,229 relating to a thermotropic copolyester having a nematic structure of the liquid crystalline phase issued. It was derived from a saturated aliphatic dicarboxylic acid, a 4,4'-dihydroxybiphenyl, and a p-hydroxybenzoic acid.